West Nile virus infections soar in California

Updated 8:13 am, Thursday, September 4, 2014

The number of mosquitoes infected with the potentially deadly West Nile virus is at the highest level ever detected in California, leading to an increase in the disease in humans, state health officials said Wednesday.

So far this year, 181 cases of West Nile in humans have been reported to the California Department of Public Health, a significant increase over the 101 cases reported this time last year. Just last week, state officials said they received reports of 52 new cases.

"We expect to see more people become infected as this is the time of year when the risk of infection is the highest," Dr. Ron Chapman, director of the state's Public Health Department, said in a statement.

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Eight people have died from the mosquito-borne disease in California, compared with six at the same time last year. Six of this year's deaths occurred in the Northern California counties of Sacramento, Sutter, Shasta, Glenn and Stanislaus, where two West Nile deaths were reported. Two deaths were also reported in Orange County.

The virus has been detected in 36 of California's 58 counties this year. West Nile season typically runs from July through September. Fifteen people died from the disease last year.

West Nile virus is carried by birds, but is transmitted to humans and animals by the bite of an infected mosquito. The disease is not passed from human to human.

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Vicki Kramer, chief of the vector-borne disease section of the state health department, said the drought may be contributing to this year's high number of bird and mosquito infections.

"There is less standing water available for both birds and mosquitoes, and birds and mosquitoes are coming into closer contact as they seek out the remaining water," she said.

That translates into a higher risk for human infection, but the risk of serious illness is low for most people. Most people who are exposed to the virus never have symptoms, and some will experience flu-like symptoms such as fever, achiness and swollen lymph glands and recover on their own.

But a small number of people - less than 1 percent - can develop a serious neurologic illness, such as encephalitis or meningitis, which can lead to death. Those at highest risk of developing complications are those older than 50 with other health conditions such as diabetes, high blood pressure or both.

People who develop neurological symptoms such as confusion and muscle weakness should seek immediate medical attention.

Public health officials said people can reduce their chances of getting bit by a mosquito by using insect repellent containing DEET, picaradin, lemon eucalyptus oil or a chemical called IR3535.

Other recommendations include wearing protective clothing, especially if outside at dawn and dusk when mosquitoes are most active, making sure window screens are tight fitting, and eliminating sources of standing water such as flower pots and unmaintained pools where mosquitoes can lay their eggs.

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